Electrical devices which transform electric energy from one or more circuits to one or more other circuits through electromagnetic induction are commonly referred to as transformers. Generally, a transformer consists of two or more windings (primary and secondary, etc.) interlinked by a mutual magnetic field.
The usefulness of a transformer lies in the fact that electrical energy can be transferred from one circuit to another without direct connection, and in the process can be readily changed from one voltage level to another. Transformers are widely used in low-power, low-current applications where a large power output is required. The power output is determined by the turns ratio between the primary and secondary windings. By properly proportioning the numbers of primary and secondary turns, any desired voltage ratio, or ratio of transformation can be obtained.
A problem encountered in the field of transformers is that there is always some power loss in the resistance of the coils and in the core. As a result, the power taken from the input or source will usually exceed that taken from the secondary coil. Although power losses may be reduced by decreasing the number of turns in the coils, this approach is usually self-defeating since the voltage induced in the coils is proportional to the number of turns in the coils.
One previously known means for reducing power losses and improving the efficiency of transformers is shown in U.S. Pat. No. 1,790,906 to Eckman. In that patent, a transformer is disclosed in which the primary coil is entirely enclosed by an outer housing which also forms the secondary winding of the transformer.
Similarly, U.S. Pat. No. 2,553,665 to McKechnie discloses a transformer having a secondary winding formed from a one piece casting which has at least two complete turns. Like the Eckman transformer, The McKechnie transformer also discloses an outer housing formed from the secondary winding.
Lastly, U.S. Pat. No. 512,603 to Coffin discloses a transformer having a one piece secondary winding.
Each of the above patents discloses a transformer which incorporates a one-piece secondary winding and housing. This design improves efficiency and prevents contamination of the coils by foreign material. However, each design still requires a multiturn primary winding and a large input voltage to produce the desired power output.
It would be highly desirable to design a transformer that is highly power efficient and does not require a large input voltage or a multi-turn primary winding.